1. Field of the Invention
The present invention relates to a transmission line terminating apparatus, that transfers transparent information and alarm transfer information among printed circuit boards connected in a star-like configuration, with a packet processing IC at its center.
2. Description of the Related Art
FIG. 13 is a diagram showing one example of wiring in a prior art transmission line terminating apparatus. In the example of FIG. 13, six units (shelves) 141 to 146 are shown. Each unit contains a plurality of printed circuit boards (PCBs). Among them, a transparent signal 1 is transferred between a printed circuit board (PCB) in the unit 142 and a printed circuit board (PCB) in the unit 143 over a permanently connected line, a transparent signal 2 is transferred between a printed circuit board (PCB) in the unit 141 and a printed circuit board (PCB) in the unit 144 over a permanently connected line, and an alarm transfer signal is transferred between a printed circuit board (PCB) in the unit 145 and a printed circuit board (PCB) in the unit 146 over a permanently connected line. In this way, in this prior art example, each originating printed circuit board (PCB) is connected to its terminating printed circuit board (PCB) via a permanently connected signal line. Many types of signal lines connecting between PCBs can exist other than those shown here.
In the example of FIG. 13, the transparent signal or the alarm transfer signal is transferred only between two designated PCBs. This is not practical because the signal cannot be transferred to and from other PCBs.
FIG. 14 is a diagram showing another example of wiring in a prior art transmission line terminating apparatus. In the example of FIG. 14, units 141 to 146 are wired in a mesh-like configuration forming a matrix switch so that the transparent signals 1 and 2 and the alarm transfer signal can be transmitted from each PCB in each unit to each PCB in every other unit and vice versa.
FIG. 15 is a diagram for explaining how signal lines are wired in a prior art transmission line terminating apparatus in the case where many PCBs are mounted within one unit. In FIG. 15, interface boards (IF boards), multiplexer boards (MUX boards), and demultiplexer boards (DMUX boards) are mounted as the PCBs. The IF boards a to l are mounted on the upper rack, while the MUX boards and DMUX boards, m to x, are mounted on the lower rack.
In the illustrated example, wiring lines for transmission of the transparent signal 1 are permanently connected from the DMUX board r to the IF boards a to d.
Wiring lines for transmission and reception of the transparent signal 2 are permanently connected between the IF board a and the IF board i, between the IF board b and the IF board j, between the IF board c and the IF board k, and between the IF board d and the IF board l, respectively.
Of the wiring lines for alarm transfer, only the wiring line for transmission from the DMUX board r to the MUX board g and the wiring line for transmission from the DMUX board t to the MUX board x are permanently connected.
These wiring lines are permanently formed on the back board of the unit, and the back board is then referred to as the back wired board (BWB).
FIG. 16 is a diagram showing an example of wiring when transferring the transparent signals and the alarm transfer signal among all the PCBs mounted within the unit shown in FIG. 15. In FIG. 16, wiring lines are provided for transmission and reception of the transparent signals and the alarm transfer signal between the IF a and all other PCBS. Though not shown here, separate wiring lines for the different types of signals are also provided for each of the other PCBs for connection to every other PCB.
In the prior art configuration shown in FIG. 13, as each of the dedicated wiring lines for transmission and reception of the transparent information and the alarm transfer information among the PCBs is permanently connected, the prior art has the problem that it cannot provide a flexible network configuration that meets user customization needs.
In the prior art configuration shown in FIG. 14, since wiring lines for transmission and reception of the transparent information and the alarm transfer information have to be provided between all PCBs in every unit and all PCBs in every other unit, the problem is that the number of wiring lines becomes enormous, increasing the complexity of the entire configuration as well as the cost of the apparatus.
In the prior art shown in FIGS. 15 and 16, as the wiring lines among the PCBs are fixed, meaning that the insertion slot position for each PCB in the unit is permanently determined, any PCB cannot be inserted in any slot position, and this causes inconvenience to the operator. Furthermore, if a PCB is built to meet customer needs, the PCB cannot be inserted in the desired slot since the wiring lines are permanently formed on the BWB as earlier described. The resulting problem is that a flexible unit configuration that meets customer needs cannot be provided. Another problem is that since an enormous number of signal lines are needed, not only does the number of PCB connector pins become enormous but the amount of BWB wiring also increases, increasing the complexity and cost of the apparatus.